Accurate XY Scan by Crosstalk Elimination

Park Systems’ advanced Crosstalk Elimination (XE) scan system effectively addresses all of the above-mentioned problems. In this configuration, we used a 2-dimentional flexure stage to scan the sample in only the XY direction, and a stacked piezoelectric actuator to scan the probe cantilever in the Z direction only. The flexure stage used for the XY scanner is made of solid aluminum. It demonstrates high orthogonality and an excellent out-of-plane motion profile. The flexure stage can scan large samples (~1 kg) up to a few 100 Hz in the XY direction. This scan speed is sufficient because the bandwidth requirement for the XY axes is much lower than that for the Z axis. The stacked piezoelectric actuator for the Z-scanner has a high resonance frequency (~10 kHz) with a high pushpull force when appropriately pre-loaded.

XE scan system

independent, loop XY and Z flexure scanners for sample and probe tip

XY flexure scanner

Flat and orthogonal XY scan with low residual bow

XE-Peformence

Figure 9. Zero background curvature by Park Systems XE-system (a) and typical background curvature of a conventional AFM system with a tube scanner (b). (c) shows the cross section of these background curvatures.

Figure 9. shows unprocessed AFM images of a bare silicon wafer taken with the XE-system (a), and with a conventional AFM (b). Since the silicon wafer is atomically flat, most of the curvatures in the image are scanner-induced artifacts. Figure 9. (c) shows the cross section of the images in Figure 9. (a) and (b). Since the tube scanner has intrinsic background curvatures, the maximum out-of-plane motion is as much as 80 nm when the X-axis moves 15 μm. The XE scan system has less than 1nm of out-of-plane motion for the same scan range. Another advantage of the XE scan system is its Z-servo response.

Figure 10. Figure 11.

Figure 10. is an image of a porous polymer sphere (Styrene Divinyl Benzene), whose diameter is about 5 µm, taken with the XE-system in Non-Contact mode. Since the Z-servo response of the XE-system is very accurate, the probe can precisely follow the steep curvature of the polymer sphere as well as small porous surface structures without crashing or sticking to the surface. Figure 11. shows another example that demonstrates the high performance of the z-servo response with a flat background.

Best Life, by True Non-Contact™ Mode

In True Non-Contact™ Mode, the tip-sample distance is successfully maintained at a few nanometers in the net attractive regime of inter-atomic force. The small amplitude of tip oscillation minimizes the tip-sample interaction, resulting in superb tip preservation and negligible sample modification.

True Non-Contact™ Mode

Tapping Imaging

Quick tip wear = Blurred low-resolution scan

Destructive tip-sample interaction = Sample damage and modification

Highly parameter-dependent

Longer Tip Life and Less Sample Damage

The sharp end of an AFM tip is so brittle that once it touches a sample, it becomes instantly blunt and limits the resolution of an AFM and reduces the quality of the image. For softer samples, the tip will damage the sample and also result in inaccuracies of sample height measurements. Consequently, preserving tip integrity enables consistent high resolution and accurate data. True Non-Contact Mode of theXE-AFM superbly preserves the tip, resulting in much longer tip life and less sample damageThe figure, displayed in 1:1 aspect ratio, shows the unprocessed raw data image of a shallow trench isolation sample imaged by the XE-AFM, whose depth is also confirmed by scanning electron microscope (SEM). The same tip used in the imaging of the sample shows no tip wear even after taking 20 images.

Park XE7 features

2D Flexure-Guided Scanner with 10 µm x 10 µm Scan Range

The XY scanner consists of symmetrical 2-dimensional flexure and high-force piezoelectric stacks provides high orthogonal movement with minimal out-of-plane motion as well as high responsiveness essential for precise sample scanning in the nanometer scale. The compact and rigid structure was designed for low noise, high speed servo response.

Flexure-Guided High Force Z Scanner

Driven by a high-force piezoelectric stack and guided by a flexure structure, its rigidity allows it to move at higher speeds in the vertical direction than the scanners used in conventional AFMs. The maximum Z scan range can be extended from 12 µm to 25 µm with the optional long range Z scanner (optional).

Slide-to-Connect SLD Head

The AFM head is easily inserted or removed by sliding it along a dovetail rail. The low coherency of the Super Luminescence Diode (SLD) enables accurate imaging of highly reflective surfaces and precise measurements for pico-Newton Force-distance spectroscopy. The SLD wavelength eliminates interference issues for users interested in combining the AFM with experiments in the visible spectrum.

Accessible Sample Holder

The unique head design can handle up to 100 mm sample size and allows for easy side access to the sample and tip.

Manual XY Sample Stage

The measurement location of the sample is easily and precisely controlled by the manual XY stage. The travel range of the XY sample stage is 13 mm x 13 mm.

Manual Optics Stage

The focus mechanism for the on-axis optics is adjusted manually.

Park XE Control Electronics with DSP Board in Controller

The nanoscale signals from the AFM are controlled and processed by the high performance Park XE electronics. With its low noise design and high speed processing unit, Park XE electronics successfully realize True Non-Contact™ mode ideal for nanoscale imaging as well as precise voltage and current measurement.